class_docstr: Piecewise constant decay with warmup schedule.
code: def get_config(self):
      return {
          "rescaled_lr": self.rescaled_lr,
          "step_boundaries": self.step_boundaries,
          "lr_values": self.lr_values,
          "warmup_steps": self.warmup_steps,
          "compute_lr_on_cpu": self.compute_lr_on_cpu,
          "name": self.name,
      }
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import os
  from absl import flags
  import numpy
  import tensorflow
  from tensorflow.python.keras.optimizer_v2 import gradient_descent
  from utils.flags import core
  from utils.misc import keras_utils
label_desc: Use image node_id 4 for calling the PiecewiseConstantDecayWithWarmup obj's underlying member method code with example usage: obj.get_config() and returns: dict